Dynamic power consumption is an ongoing concern for integrated circuit (IC) devices, especially with the ever-increasing clock frequencies used in synchronous IC devices. Indeed, for some IC devices, more than half of the total dynamic power consumption may be attributed to clock distribution networks. One technique to reduce the dynamic power consumption of clock distribution networks is to employ clock-gating circuits (CGC) that selectively gate a number of clock signals on the IC device. More specifically, clock-gating circuits may reduce power consumption by selectively pruning an IC device's clock tree, thereby disabling portions of the clock tree so that circuit elements such as latches and/or flip-flops associated with the disabled portions do not switch between logic high and low states. Thus, preventing such latches and/or flip-flops from toggling between logic states may significantly reduce dynamic power consumption of the IC device.
Unfortunately, many conventional clock-gating circuits consume an undesirable amount of dynamic power, even when disabled. For example, FIG. 1A shows a conventional clock-gating circuit 10 having two series-connected inverters INV1-INV2 that generate complementary clock signals clk_net and clk_net in response to an input clock signal clk_in. The complementary clock signals clk_net and clk_net control a pass gate 12, which provides a gating signal pn1 that is logically combined with clk_in in NAND gate 14 to generate an output signal pn2. Signal pn2 is inverted by inverter INV3 to generate the output clock signal clk. Although effective in selectively gating the input clock signal clk_in in response to a clock enable signal (clk_en), clock-gating circuit 10 undesirably consumes dynamic power because the output terminals of the series-connected inverters INV1 and INV2 undesirably toggle between logic states in response to transitions in the input clock signal clk_in.
Thus, there is a need to reduce the dynamic power consumption associated with distributed clock systems provided within IC devices.
Like reference numerals refer to corresponding parts throughout the figures.